code: def user_factor(Y, YtY, Cui, u, regularization, n_factors):
      # Xu = (YtCuY + regularization * I)^-1 (YtCuPu)
      A, b = user_linear_equation(
          Y, YtY, Cui, u, regularization, n_factors
      )
      return np.linalg.solve(A, b)
  
imports: import functools
  import heapq
  import logging
  import time
  import numpy
  import scipy
  import scipy.sparse
  from tqdm.auto import tqdm
  from ..utils import check_blas_config, check_csr, check_random_state, nonzeros
  from .None import _als
  from .matrix_factorization_base import MatrixFactorizationBase
label_desc: Use image node_id 3 for calling a global function with example usage: user_factor(Y, YtY, Cui, u, regularization, n_factors) and returns: np